1




Titration is a common laboratory technique
used to determine the concentration of a
solution
Titrant is the solution in the buret
Standard Solution a solution of KNOWN
concentration, usually in the buret
Sample is the solution being analyzed in a
titration (the “unknown” concentration)
2

Endpoint is the point at which the indicator
changes colour
Before endpoint
At endpoint
(faint pink)
After endpoint
(overshot!)
3

Equivalence Point the measured quantity of
titrant recorded at the point at which
chemically equivalent amounts have reacted
(a.k.a. the stoichiometric point)
4
5

Titration Technique Using a Buret VIDEO#1
• Titration Technique Using a Buret VIDEO#2
6


For most neutralization reactions, there is no
visible signs that a reaction is occurring
An acid-base indicator is a substance that
changes colour in acidic and basic solutions
7

Majority of acid-base indicators are weak,
monoprotic acids, the undissociated weak
acid is one colour, and its conjugate base is a
different colour
H (indicator) (aq)  H+ + (indicator)- (aq)
Colour 1

Colour 2
For example, phenolphthalein is an indicator
often used for reactions between strong acids
and bases. It is colourless between pH 0-8
and turns pink between pH 8-10
8

Endpoint is the point at which the indicator
changes colour
Before endpoint
At endpoint
(faint pink)
After endpoint
(overshot!)
9

Standard Solution is one of the reactants, you
must know the precise and accurate
concentration of the standard solution.
Titration Example
An acid rain sample containing sulfurous acid
was analyzed in a laboratory using a titration
with a standard solution of sodium
hydroxide. Use the following evidence given
in Table 1 to determine the concentration of
the sulfurous acid.
10
Table 1: Titration of 20.0 mL of H2SO3(aq)
with 0.150 mol/L NaOH(aq)
Trial
1
2
3
Final buret reading (mL)
15.3
30.5
45.5
Initial buret reading (mL)
0.2
15.3
30.5
Volume of NaOH(aq) added
15.1
15.2
15.0
11
Balanced Chemical Equation
H2SO3(aq) + 2NaOH(aq)  Na2SO3(aq) + 2H2O(l)
What was the average NaOH(aq) used to
titrate 20.0 mL sulfurous acid?
vNaOH = 15.1 + 15.2 + 15.0
3
= 15.1 mL
12
Where are you starting?
Where are you going?
H2SO3(aq) + 2NaOH(aq)  Na2SO3(aq) + 2H2O(l)
Stoichiometry Time!!!
Answer: 0.0566 mol/L H2SO3
Titration Practice (ws)
13